Echo canceller

Abstract

The present invention provides an echo canceller having a holding portion which holds at least a communication frame length's worth of reception signals; a power calculation portion which calculates power for each communication frame based on the reception signals held in this holding portion; a divider which divides, by the power calculated for each communication frame, the echo elimination residue signal for each sample of the communication frame output from a subtractor; and an update portion which updates the tap coefficients of an adaptive filter according to the output signals from the divider.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]This invention relates to an echo canceller based on a prescribed echo model.[0003]2. Description of Related Art[0004]In general receiver terminal devices, an audio signal from an exchange network is introduced via a four-line circuit, and this is supplied to many types of service by a two-line circuit. At the termination of such a communication circuit, various echo cancelling techniques are used in order to deal with impedance mismatching. These techniques are disclosed in the reference “Introduction to Adaptive Filters”, S. Haykin, Macmillan Publishing Co., New York, and elsewhere.[0005]For example, there is a technique which uses an echo canceller with the configuration shown in the block diagram of FIG. 2. In FIG. 2, this echo canceller 10 which is an example of the conventional art has a receiving signal route comprising a reception input terminal Rin 11 for reception from the exchange network, an analog / digital c...

AI Technical Summary

Benefits of technology

[0024]In order to solve these problems, the echo canceller of this invention is an echo canceller which forms a pseudo-echo signal from a reception signal using an adaptive filter, subtracts the pseudo-echo signal from the transmission signal using a subtractor, and eliminates the echo component in the transmission signal. The echo canceller of this invention has a holding portion to hold at least a communication frame length's worth of the reception signal;

Problems solved by technology

However, in the above echo canceller example of the prior art, the tap coefficients Hk(n) are calculated using equations (3) and (4), and so the following problems arise from the large amount of calculations.

Because this preprocessing is also executed by the DSP as part of the division operation, there is the problem that even a single division operation can impose an extremely large burden on the DSP.

However, if division is performed each time a delay sample is introduced, a large part of the allowed calculation amount will be consumed by division operations.

Hence there is the problem that a large calculation capacity cannot be left for the above-described vital multiply-accumulate operations.

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